The preparation of herbal products can be an amazing and fulfilling personal journey. With common sense and some well thought out and documented testing methods, consistent, high quality herbal formulations can be assured.
We’ve listed some methods below that can be incorporated into a manufacturing process. KB Analytical / The Herbalist’s Chemist can help you develop and implement a coherent and comprehensive program to help you navigate through the regulatory maze.
Light, temperature, humidity, and milling are very important physical conditions that should be considered before proceeding with any preparation process. Each of these storage items can have a significant impact on the quality and consistency of the finished product. Even if the storage conditions are carefully controlled, it is recommended that collected plants be processed and used as soon as practical to avoid any decomposition.
Once storage has been addressed, testing of the product should be considered. The testing procedure should complement the type of plant and/or product being prepared. Most herbal monographs suggest the appropriate tests specific to a plant. In most cases, the primary identification methods, either microscopic, TLC, or both are always used. If warranted, these primary methods can then be supported by one or more of the quantitative methods listed below.
Testing of the final herbal preparation (tincture; salve; etc) is the next step requiring analysis. The choice of analyses depends on the intent of the preparation. For example, if a concern is the efficiency of a tincture extraction (to determine if a compound/s have been successfully extracted) then TLC should be performed. If routine total solids or total extractables are used to confirm that these results meet the preparer’s specifications then these should suffice.
1) Microscopic: A well documented and valued means of examination and identification.
Looks at various cells, cell structures, and organelles of a plant.
2) Thin Layer Chromatography: A primary identification method that can distinguish both compound classes and specific compounds contained in a plant. Uses chromatography, a technique which separates compounds by several chemical means including polarity.
Detection is very versatile using many derivatization schemes.
3) HPLC: A more instrument specific, inline chromatography method for the fingerprinting and quantitation of compounds contained in a plant.
Detection is typically limited to UV or pre/post derivatization.
A representative sample is dried under various, specified conditions to a constant weight. Drying conditions may be a desiccator, in a vacuum, or in an oven.
The result indicates the amount of weight loss at a specified temperature due to moisture and volatile compounds.
2) Foreign matter: A representative weight of the sample is spread out as a thin layer on a clean, light work surface. Visible inspection by eye or aided by a hand lens is used to separate any atypical or foreign matter. Any foreign matter that is collected is weighed and used to calculate percentage observed in the sample.
The results show any material not typical of the plant material.
3) Total ash: A representative sample is added to a platinum crucible and heated to 600C in a muffle furnace until a constant weight is attained. Can be followed by Ash insoluble in hydrochloric acid.
The results show the compounds (mainly inorganic) that are contained in the plant.
4) Total solids: A representative volume of sample (tincture) is introduced into a tared drying dish and dried at a specified temperature. The resulting residue weight is used to calculate the total solids contained in the sample.
This test can be very useful in comparing extractions or decoctions from batch to batch.
5) Ethanol / water soluble extractives: A representative sample introduced into a flask containing a specified concentration of ethanol/water, shaken and allowed to settle for 24 hours. The residue is filtered and washed, dried and weighed. The resulting weight is used to calculate the extractives. A chloroform/water mixture is used in place of ethanol for the water solubles.
This is a quick method to determine the yield of soluble compounds from plant material using various solvents.
6) Volatile oils: A calibrated steam distillation apparatus is used to determine the yield of volatile oils contained in a sample.
7) Refractive index of glycerite or ethanolic tinctures: A refractive optical method to quickly determine the alcohol/water or glycerine/water ratio in a tincture preparation.
8) Trace metals: Electrothermal or electrochemical methods can be used to determine the concentration of heavy metals such as lead, cadmium, arsenic, and mercury contained in the plant material.
Any or all of the methods above can be incorporated in a cGMP plan designed for product preparations.